Can Asteroid Mining Solve The Rare Metal Shortage?

By Wade Lanning

The privatised space race has reignited the idea of asteroid mining for resources

This
may sound like science fiction but, since at least the 1970s, organisations like NASA
have been considering the possible advantages of asteroid mining for
resources. In this article for the materials
search engine Matmatch, guest author Wade Lanning, PhD in materials
science and engineering, explains that, while space travel is still
extremely risky and expensive, certain advantages make asteroid mining an
appealing possibility.

Metallic_asteroids (300 dpiX): Metallic asteroids are primarily iron and nickel but can contain rare metals like platinum, gold, iridium, palladium, osmium, ruthenium and rhodium at concentration several times higher than what is found on Earth

In the midst of a new privatised
space race, companies are revisiting the possibility of sourcing materials from
outer space — not least because earth faces a global rare metal shortage. A
single asteroid could contain trillions of dollars’ worth of precious metals,
and sourcing materials from asteroids could enable large-scale construction in
space.

The world demand for rare and
precious metals is growing, and a mix of political turmoil and natural scarcity
are contributing to fears that the global
supply will be unable to keep up.
As supplies dwindle, demand grows, and prices rise, the new private
company-based space race might offer a solution to the shortage.

The asteroid mining would require
major investments in new technologies, but there has been enough interest that companies
have been formed to prospect for asteroids
to harvest.

Asteroids can be grouped broadly
into those that are primarily carbonaceous, silicates, or metallic. Metallic
asteroids are primarily iron and nickel but can contain rare metals like platinum, gold, iridium, palladium, osmium, ruthenium and rhodium (see the links to find properties of these materials) at concentration several
times higher than what is found on Earth.

Bringing rare metals to Earth is
not the only possible use for asteroid-derived materials. Building equipment on
Earth then lifting it into space is, in fact, expensive. Every kilogram of
material costs
money to lift into orbit, and individual
space launches cost upwards of $100
million USD. So, even the more common
materials in asteroids, like iron
and nickel, take on new value because they are already in outer space.

Other materials without an obvious
structural purpose, such as water, could be used as raw materials for fuel
synthesis and/or life-sustaining supplies. If the materials found in asteroids
could be processed into a useable form in space, it would remove a major
barrier to large-scale construction and exploration in outer space.

Surveying for
valuable ores

Harvesting an asteroid for
trillions of dollars’ worth of platinum sounds exciting. Yet the reality is
that, so far, humans have barely harvested a few dust particles from actual
asteroids.

Much of the in-depth information we
have on the composition of asteroids is from the characterisation of meteorites that have, of course, fallen to Earth from space. So how could we
possibly know which asteroids are worth mining?

The vast majority of measurements
of the composition of asteroids in outer space
have been accomplished using infrared spectroscopy via telescopes. Asteroids
with different compositions absorb different frequencies in the infrared
spectrum, allowing scientists to determine what they are made of based on the
light they reflect.

More recently, radar-based
techniques have also been deployed to distinguish different types of an
asteroid. Such estimates
of asteroid composition are often calibrated
against samples of meteorites found on Earth.

The relatively high abundance of
rare metals in asteroids allows them to be ranked according to their
approximate value and relative
difficulty to harvest. A few companies have even been
founded to explore the possibility of
extracting heavy metals from near-earth asteroids (NEAs).

A 2012
feasibility study at the California Institute
of Technology (CalTech) in Pasadena, US, argues that the most attainable first
mining project would consist of bringing an NEA into high-lunar orbit, and making
it accessible for surveying and material extraction. They estimated that it
would be feasible to redirect an asteroid approximately 7 m across to orbit the
moon by 2025. However, the same study estimates the cost of the mission to be
at least $2.6 billion USD.

Bringing an asteroid close enough
to Earth to extract valuable materials depends on more than just the distance
and size of the asteroid. One of the most important factors is the change in
the asteroid’s velocity, or “delta V”, which would be required to alter the
asteroid’s trajectory to one that would put it in orbit around Earth or the moon.
The amount of fuel required to push the asteroid would depend on both the
asteroid’s mass and delta V.

Other factors, like the asteroid’s
spin and whether or not it is travelling in an asteroid pair, also factor into
the difficulty of re-directing the asteroid to a location for harvesting.

Thus, any given asteroid’s
trajectory, mass, spin and more must be taken into account when planning a
retrieval operation. Additionally, any missions must also be timed to take
advantage of periods when the asteroid is already moving closer to the Earth.

How close are we?

In order to understand how much
additional research and effort may be required to make harvesting asteroids a
reality, we should take a look at the history of human efforts to retrieve
materials from space for scientific study.

By far the largest amounts of
samples ever recovered from outer space were achieved during the race to the
moon between the USA and USSR during the 60s and 70s. NASA retrieved a total of
382
kg of material from the Apollo missions
between 1969 and 1972.

Automated “Luna” spacecraft sent by
the USSR also brought back about 300 g worth of samples. It took another 30
years before any other serious efforts to retrieve material from space were
attempted.

The dust was successfully returned
to Earth. The material collected resulted in some valuable scientific
discoveries; but grabbing a few tiny
micron-sized particles is a long way from industrial-scale mining.

The Japan Aerospace
Exploration Agency (JAXA) has executed the most successful missions to retrieve
material from asteroids so far. While the Hayabusa
1 mission to 25143 Itokawa asteroid
encountered difficulties and was only able to return with some dust particles,
the Hayabusa
2 mission currently underway to explore and
sample the NEA, 162173 Ryugu.

The probe was launched carrying three
small rovers, a landing module, and equipment for taking surface samples. It
has already completed two sampling runs, where it blasted
the asteroid with a tantalum projectile then
collected the flying debris. Hayabusa 2 is expected to return home in December
of 2020 and the samples it carries will be the largest payload of samples
retrieved from a near-Earth body since the Apollo missions.

NASA also has ongoing missions to
take samples from NEAs. The OSIRIS-REx probe is currently orbiting an NEA, Bennu, where it will map the surface and
retrieve samples.

The sample
retrieval operation will be a precise manoeuvre
whereby the probe approaches Bennu on a trajectory that matches the asteroid’s
spin, touches the surface with a sample collector for about five seconds, and
uses a jet of nitrogen to flush loose dust and pebbles into traps in the
collector. Both the Hayabusa and OSIRIS-REx missions represent major
advancements in our knowledge of how to manoeuvre a vehicle in proximity to an
asteroid.

By
some calculations, Ryugu and Bennu are in the
top five most economically viable asteroids for mining efforts. Ryugu has an
estimated value of more than $80 billion USD while Bennu is with about $670
million USD.

However, they would cost about $50
billion and $485 million to harvest, and those estimates are from Planetary
Resources, a company whose existence is
predicated on the idea that asteroid mining will be feasible soon. After the
Hayabusa and Ryugu missions are concluded, we will have more detailed information
about their compositions than ever before, and we will see whether they are as
rich in precious metals as speculators hope.

The biggest step towards converting
asteroids into a harvestable resource may be the upcoming “Double Asteroid
Redirection Test” or DART. Scheduled to launch in 2021, the DART
mission will involve the asteroid pair
65803 Didymos. The DART vehicle will launch a tiny observer satellite, then it
will accelerate towards one of the 65803 Didymos asteroids while taking
pictures, then collide with the asteroid.

Observations from Earth-based
telescopes and the microsatellite will monitor the change in the asteroid’s
trajectory relative to its twin. This could be the first step towards
redirecting asteroids that pose a threat to Earth or towards moving an asteroid
into a convenient position for mining.

High costs, high
risks but high rewards

So, will the world economy soon be
flooded by a vast new supply of previously-scarce precious metals? Probably
not. At present, no company is quite
ready to risk billions of dollars on a venture that requires technologies which
have not been fully developed and techniques that are not proven.

The nearest thing humans have
accomplished so far is scraping a few tiny samples off of an asteroid’s
surface, and even those missions were very risky and challenging. However,
asteroid mining might still have a future.

In the next few years, missions
like Hayabusa 2 and OSIRIS-REx will be returning to earth with their asteroid
material samples. The data from those missions, DART and others will grant us a
new understanding of how to manoeuvre vehicles around asteroids and change the
trajectory of the asteroids themselves.

Global demand for technologically-critical metals is still growing. In the meantime, new NEAs are constantly being discovered, and so is our ability to detect valuable metals in those asteroids. If these trends continue, it may only be a matter of time until an asteroid with enough precious metals passes near the Earth and someone decides it’s worth the risk to try to catch it.